4 Answers
4

This is a bit of a minefield you've strayed into and it's prone to religious warfare. Here's my take on these issues:

Is it a legal issue? This would very much depend on where you are, where your servers are, where your customers are and the relevant laws in each of these jurisdictions. There is some evidence that this can be a legal issue but I don't know how much stock to put into this. It sounds like really dubious territory to me, but IANAL and all that jazz.

Is it a moral / ethical issue?To some it is. To some it is the same sort of issue as putting ramps for wheelchairs or the like in brick and stone shopping fronts. The argument goes that the Internet is a major economic force and it is unfair and unethical to make a significant portion of the population unable to access that economic opportunity.

Is it a user ability issue? It is, and the W3C seems to think it's sufficiently important to actually post a technical recommendation about it. In the end it remains, however, a decision that you will have to make (keeping in mind any possible legal threats) before deciding if it's worth the effort or not.

Is it a maintainability issue? I've not heard this argument before, but I can see how proper use of CSS and tags could make a site both more maintainable and more accessible. Still, this seems to be a pretty weak justification overall to me.

Working right now on improving the accessibility of our website, I can say that the maintanability effort goes up. Specific work-arounds / design / thoughts are required to be more accessible, and this inherently adds some complexity.
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Matthieu M.Jun 17 '11 at 16:39

You don't want to be cutting off a significant proportion of your potential market.

People with disabilities make up a significant proportion of the general population so if you are designing a reasonably universal web site (Amazon, Facebook, IMdB at the extreme) then you will be shutting out a lot of users if you don't. These are users that have credit cards (or access to credit cards) the same as the rest of the population and want to spend their money. You should let them spend it with you.

It's a similar situation to vegetarian options on menus (at least in the UK). There's been a significant rise in the number of vegetarians so it makes commercial sense for restaurants to cater for them.

+1 for a good argument, though I've never personally been convinced that most of the "accessibility" features help much since disabilities are very different and have very diferent requirements. For example, my dad is slightly visually impaired but none of the tagging etc. is at all helpful... the main thing he needs is a decent zoom mode in the browser.
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mikeraJun 17 '11 at 13:18

Short version, if you don't personally know everyone who's going to use the software then yes, you need to take into account that not everyone can read 6pt fonts, that people are color-blind, and many other factors.

No, it's clearly not possible to support all disabilities, but incorporating accessibility early on helps increase the number of people who use and enjoy using your site. As @Crazy Eddie points out, it's also useful for things like testing.

Based on my entirely unscientific observations of web developers, i would say that accessibility is used as a smokescreen to steer the client into letting them Do Things Properly - using semantic page structure, carefully-designed CSS, throwing away all the kipple the last guy wrote, etc.

As a programmer, i am strongly in favour of Doing Things Properly, and familiar with the problem of getting the guys with the chequebook to agree to it, so i have a great deal of sympathy for this. I just wish i had a corresponding manoeuvre for code.